Adjustable beds, such as those in hospitals and nursing homes, generally include some mechanism for elevating the head portion of the bed. Raising this segment serves a number of different purposes. Commonly, elevating the head allows the use of the bed for such normal daily activities as eating, reading, watching televsion, and others. However, frequently the bed's occupant, with his toro elevated, tends to slide towards the foot of the bed due to gravitation. Elevating the knee portion of the bed helps to preclude this sliding.
Other situations may require an elevation of the head but with the knee remaining flat. One example includes a patient having undergone recent surgery of the lower abdominal area. Elevating the knee portion of this patient may place an undesirable strain upon the tissues in the incisional area.
Furthermore, the knee should remain flat for patients with circulatory problems in order to prevent or minimize clotting in their lower extremities. Also, a slight elevation of the head with no knee elevation improves the drainage removal of congestion for patients with respiratory ailments.
Orthopedic patients having a straight cast on a broken leg cannot have their knees elevated although they may wish to sit up by raising the head portion of the bed. Moreover, elevating the head but not the knee allows more facile entrance into and exit from the bed of a patient who has difficulty maneuvering.
Consequently, a number of beds have afforded a choice between the knee section remaining flat as the head section raises or the knee following the head section in coordinated motion. Nonetheless, they have suffered from such drawbacks as complicated and expensive mechanisms interconnecting the head and knee portions of the bed. Some have required an unacceptable exertion when manipulating the appropriate mechanisms to achieve the desired results.
With regards to the latter, E. C. Ortmeier, in his U.S. Pat. No. 1,658,736, shows a bed in which the knee must raise with the head to some extent before it can disengage and return to the flat position. Specifically, once elevated slightly, the operator must physically lift up the foot of the bed and remove it from the mechanism which flexes the knee. Aside from the physical burden of lifting the actual portion of the bed, this procedure also presents the danger of entrapping and injuring fingers. Moreover, after the head reaches its lowest position, the bed requires a repetition of the foregoing procedure to again disengage the knee-raising mechanism.
U.S. Pat. No. 3,398,411 to J. Douglass, shows a bed in which the knee-adjusting mechanism connects to the actual head portion of the bed itself. This structure, which thus must support the load of the knee portion, entails an appreciable added expense to the construction of the bed.
C. W. Pratt, in his U.S. Pat. No. 474,690, shows a bed which he attempts to convert into a chair by allowing the feet to lower as the head rises. By not allowing the knee portion of the bed to raise, the altered configuration aggravates the gravitation of the patient as well as the mattress to the foot of the bed, rather than precluding it. The modern efforts have rejected this early concept when providing a bed-ridden patient with a configuration in which to conduct daily activities.
In F. J. Burst et al.'s bed, disclosed in their U.S. Pat. No. 3,821,821, the entire mattress moves towards the head of the bed as the head portion raises. This, of course, allows the patient to remain near to the usual accessory equipment found at this end of the bed. The relative motion between two bed frames accomplishes this movement of the mattress. The knee adjusting mechanism utilizes this relative motion between the frames in order to, when desired, elevate the knee when the head rises. This device represents a significant accomplishment in the field of adjustable beds, but only has pertinence to those beds with the moving frames.
Consequently, the search continues for a mechanism that permits the knee section, when desired, to elevate with the head section while obviating the drawbacks of the previous devices.